Method and apparatus for monitoring the bonding of paper-wrapped wire

ABSTRACT

IN A DEVICE FOR APPLYING ADHESIVE TO THE LONGITUDINAL EDGE OF A PAPER TAPE BEING WRAPPED AROUND AN ADVANCING WIRE, INTERRUPTIONS IN ADHESIVE FLOW TO THE TAPE ARE SENSED FROM A DECREASE IN ELECTRICAL CONDUCTIVITY AT A POINT IMMEDIATELY DOWNSTREAM OF THE APPLICATOR.

May 11, 1971 GREGG ETAL 3,578,518 METHOD AND APPARATUS FOR MONITORING THE G BONDING 0F PAPER-WRAPPED WIRE Filed June 27, 1968 2 Sheets-Sheet 1 IN VliN'l'U/(S R ALVIN L. GREGG CHARLES E. KOONS Z-Sheets-Sheef 2 A. L. GREGG ETAL" BONDING OF PAPER-WRAPPED WIRE METHOD AND APPARATUS FOR MONITORING THE Filed June 27. 1968 INVIL N'IORS ALVIN L. GREGG CHARLES E. KOQNS BY M 7 Mi ll/f/I? IMTIW United States Patent 3,578,518 METHOD AND APPARATUS FOR MONITORING THE BONDING OF PAPER-WRAPPED WIRE Alvin L. Gregg and Charles E. Koons, Harrisonville, Mo., assignors to Anaconda Wire and Cable Company Filed June 27, 1968, Ser. No. 740,563 Int. Cl. H01b 13/10 US. Cl. 156-64 4 Claims ABSTRACT OF THE DISCLOSURE In a device for applying adhesive to the longitudinal edge of a paper tape being wrapped around an advancing wire, interruptions in adhesive flow to the tape are sensed from a decrease in electrical conductivity at a point immediately downstream of the applicator.

BACKGROUND OF THE INVENTION In an application Ser. No. 739,757, filed June 25, 1968, assigned to the assignee of the present invention an apparatus is described for applying adhesive to the edge of a paper tape that has been applied straight-away as insulation to a telephone wire. The tape is applied by means of a die such as that described in Pats. 3,337,386 or 3,340,113, and the present invention is directed to means for detecting any failure of the apparatus to apply the adhesive. The adhesive is used in the form of a water emulsion that is supplied through a fine bore that may easily become plugged, and the quantity applied is so minute that it is not visible, particularly at high insulating speeds and very small tape widths for which the present invention has particular application.

SUMMARY We have invented a method of detecting the malfunction of an apparatus that applies adhesive to the paper wrapping surrounding an advancing wire. According to our method, during the application of the adhesive, an electrical potential is applied between two points, immediately downstream of the point of adhesive application, that are in contact with the wrapping. This application of electrical potential causes current to flow through the paper that has been wetted by the adhesive. In the practice of our method, one of the contact points for the application of electrical potential may advantageously comprise the surface of the wire. In our method we then sense reductions in the current due to interruptions in the application of the adhesive.

We have also invented an apparatus which we prefer for the practice of our method where the wire and its surrounding tape is advancing from a device that comprises means for lifting the edge of the tape from the wire and applying an adhesive. This apparatus comprises an elongated electrode mounted in electrical contact with the paper under its edge at a point downstream of the application, the adhesive vehicle not having fully evaporated at this point. It also comprises a second electrode mounted in electrical contact with the wire, and means for applying an electrical potential between the first and second electrodes. This potential results in current between the electrodes due to adhesive being applied to the paper. Our apparatus comprises means for amplifying this current and signal means responsive to decreases in the amplified current whereby interruptions in the application of adhesive are made known.

In a preferred embodiment of our invention, where the whole device is driven by a motor, we include timing means, and switch means for the motor that is controlled by the timing means. The timing means is actuated by a 3,578,518 Patented May 11, 1971 decrease in the amplified current sustained for a preselected period of time to open the switch means and thereby stop the operation of the device.

By means of our invention we are able to prevent the production of long lengths of taped wire from which adhesive is lacking.

Furthermore, by means of our invention we are enabled to operate a large plurality of adhesive applicators under the guidance of a single operator, and still maintain a very low incidence of substandard production.

In addition, our invention has been so conceived that it provides fail-safe operation of the adhesive detecting system. A more thorough understanding of our invention will be obtained from a detailed study of the embodiment shown in the appended drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows a schematic representation of the circuitry of our invention along with sections of paperwrapped wire and electrodes applied thereto.

FIG. 2 shows a diagrammatic side view of the apparatus of our invention in a preferred embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 2 an adhesive applicator 11 is applying adhesive to a paper tape wrapping 12 (FIG. 2) applied around a wire 13 in a die 14. The wire is supplied from a grounded reel 16 and the tape for the wrapping 12 is supplied from a pad 17. The die 14 spreads an edge 18 of the wrapping 12 open and deposits a fine line of vinyl acetate suspended in water at a point 19 on the inside of the lifted edge which is subsequently pressed closed again by a die 21 through which the wrapped wire passes. Between the dies 11 and 21 we have mounted a contact probe 22 with a lead line 23 joining it to the circuit indi cated generally by the numeral 24. The wire 13 is drawn, along with a similar wire 26 through the apparatus so far described by a capstan 27 driven by a motor 28 supplied by electric supply lines 29 through a switch 31 that is operated by a relay 32 (FIG. 1) within the circuitry 24 as shall be more fully described. The paper of the tape wrap 12 is cellulosic paper but other forms of paper capable of being wetted by an electrically conducting adhesive may also be used within the scope of our invention and the word paper will be understood to include such other papers, such as polyolefin and glass fiber papers, when used herein.

Referring to FIG. 1 a subcircuit indicated generally by the numeral 33 will be described in detail. This circuit is connected to the probe 22 which is used to monitor the wrapping 12 on the wire 13. It will be understood that the detailed description will apply equally well to a duplicate subcircuit, indicated generally by the numeral 34 for a probe 36 to monitor the application of adhesive on the wire 26 which is taken up with the wire 13 to form a telephone pair. Where a cable is to be formed of quads the extension of the circuitry hereinafter described to encompass four subcircuits will be obvious from the information herein given.

The probe 22 is connected through a 1000-ohm resistor 37 to an amplifying circuit comprised of npn transistors 38, 39 connected as shown with the transistor collectors both connected through the coil of a signal circuit relay 41 and push button 42 to one terminal of a l-megohm linear rheostat 43 in parallel with a 2-microfarad condenser 45 and variably grounded through a 10,000 ohm resistor 44. The emitter of the transistor 39 is connected to the other terminal of the rheostat 43 through a forty-seven ohm resistor 46 and a 20,000 ohm variable linear resistor 47. Full-wave rectified current is supplied to the circuit through rectifiers 48, 49 from a control transformer 51 energized from a 110 v. conventional A-C supply source 52 through a 0.5 ampere fuse 53. The source 52 is connected through switches of the relay 41 to a signal light 54. A timer 56 energized from the source 52 through the normally closed blade of the relay 41 is integrally associated with the relay 32 in a timed delay relay such as the relay sold by Potter and Bromfield division of American Machine and Foundry Co. as catalog number CHB-38-70001. This will open the switch 31 and stop the motor 28 if the signal light 54 or its counterpart in the circuit 34 is continuously ofi for a preselected time of 1-10 seconds.

OPERATION In operation our detector may be used with wires of different sizes and employing greater thickness and widths. The detecting operation is initiated after the adhesive applicator is working by depressing the push button 42, and, of course, its counterpart in the circuit 34. This permits current to pass through the coil of the relay 41 to energize the relay and connect the switch to the light 54 which, preferably, is green and indicates a safe condition. The variable resistors 43 and 47 are adjusted so that the light 54 goes out promptly when the flow of adhesive is deliberately interrupted and goes on again promptly when the flow is resumed. When no adhesive is flowing the electrical resistance between the electrode 22 and a point on the wire 13 separated from it by one or two thicknesses of paper tape plus an air gap is measured in hundreds or thousands of megohms. When the paper is wetted, however, capillary absorption of the water vehicle rapidly reduces this resistance below one megohm in a manner that can be sensed by our apparatus. Since the adhesive is supplied through a capillary bore, momentary interruptions of flow are unavoidable and essentially do no harm and it would not be practical to stop the motor 28 and interrupt the processing of wire because of such interruptions. If, however, the flow of adhesive stops for one or two seconds so that several feet of wire have passed through the operation without adhesive it is necessary to stop the machine until the cause of the malfunction has been determined. Due to the fact that the relay 41 has a double throw switch, when the circuit to the light is open the circuit to the timer 56 is closed and a timing cycle is initiated which will open the switch 31 to the motor 28 if it continues for two seconds, or some other preselected number of seconds.

We have invented a new and useful method and apparatus for monitoring an adhesive applicator of which the foregoing description has been exemplary rather than definitive and for which we desire an award of Letters Patent as defined in the following claims.

We claim:

1. The method of detecting the malfunction of an apparatus applying adhesive to the paper wrapping surrounding an advancing wire comprising the steps of:

(A) during the application of said adhesive applying an electrical potential between two points in contact with said wrapping immediately downstream of the point of said application, thereby causing an electrical current to flow through said paper wetted by said adhesive,

(B) sensing a reduction in said current due to an interruption in the application of said adhesive.

2. The method of claim 1 wherein one of said points comprises the surface of said wire.

3. In a device for bonding the longitudinal edge of a paper tape surrounding advancing wire comprising means for lifting said edge from said wire and applying adhesive comprising a volatile, electrically-conducting vehicle between said edge and said wire, an apparatus for detecting interruptions in the application of said adhesive comprising:

(A) an elongated electrode mounted in electrical contact with said paper under said edge at a point downstream of said application, said vehicle not having fully evaporated at said point,

(B) a second electrode mounted in electrical contact with said wire,

(C) means applying an electrical potential between said first and second electrodes, said potential resulting in a current between said electrodes due to said adhesive being applied to said paper,

(D) means amplifying said current,

(E) signal means responsive to decreases in said amplified current, whereby interruptions in the application of adhesive are made known.

4. The apparatus of claim 3 comprising a motor driving said device, timing means, switch means for said motor controlled by said timing means, said timing means being actuated by a decrease in said amplified current sustained for a preselected period of time to open said switch means and thereby stop the operation of said device.

References Cited UNITED STATES PATENTS 

